Automatic recognition of colors

ABSTRACT

The invention refers to a method for the automatic recognition of coloring dyes, for instance in a drawing, by illuminating the sample by a beam of light of known characteristics and by analyzing the light reflected in a number of primary colors or wave lengths, recognition of the dye from which the light is reflected being based on the position of the point which represents the responses of the photo-sensitive analyzing means corresponding to each primary color in a system of coordinates having a number of axes equal to the number of said primary colors. According to the invention the real locus (surface or volume) of all possible representative points is determined for each dye, lines or surfaces are drawn to pass between these loci, these lines or surfaces are each represented analogically by electronic circuits receiving as inlet signals the responses of the photo-sensitive means to emit a zero outlet signal for a point which would be situated on this line or surface and the position of the representative point of an unknown dye is deduced from the signs of the outlet of these circuits. Alternatively the dyes are considered by pairs in a number of two-dimensional coordinate systems.

United States Patent [191 Frappe r [451 Aug. 14, 1973 [30] ForeignApplication Priority Data Nov. 30, 1970 France 7043976 [52] US. Cl....356/176, 8/25, 250/226 [51] Int. Cl. G01] 3/46, G01j 3/42 [58] Field ofSearch 356/173 T; 8/25;

[56] References Cited OTHER PUBLICATIONS Seaton, Intl Dyer & TextilePrinter July 5, 1968, pp. 20-22.

Primary Examiner-RonaldL. Wibert Assistant Examiner-R. J. WebsterAtt0rney-Arthur E. Dowell, Jr. et al.

[57] ABSTRACT The invention refers to a method for the automaticrecognition of coloring dyes, for instance in a drawing, by illuminatingthe sample by a beam of light of known characteristics and by analyzingthe light reflected in a number of primary colors or wave lengths,recognition of the dye from which the light is reflected being based onthe position of the point which representsthe responses of thephoto-sensitive analyzing means corresponding to each primary color in asystem of coordinates having a number of axes equal to the number ofsaid primary colors. According to the invention the real locus (surfaceor volume) of all possible representative points is determined for eachdye, lines or surfaces are drawn to pass between these loci, these linesor surfaces are each represented analogically by electronic circuitsreceiving as inlet signals the responses of the photo-sensitive means toemit a zero outlet signal for a point which would be situated on thisline or surface and the position of the representative point of anunknown dye is deduced from the signs of the outlet of these circuits.

Alternatively the dyes areconsidered by pairs in a number oftwo-dimensional coordinate systems.

8 Claims, 13 Drawing Figures Pmmmwm ma 37521590 sum 1 or 3 0 INVENTOR.

AUTOMATIC RECOGNITION OF COLORS The present invention relates to theautomatic recognition of colors, as for instance by means ofphotoelectrical devices.

The problem of the automatic recognition of colors, or more exactly ofcoloring dyes, arises in many practical cases, as for instance in thereading-in of the designs used in the preparation of perforated cards orhands for loom Jacquards. In such designs the various weaves areindicated by different colors each resulting from the use of aparticular dye. A skilled reader distinguishes readily the variouscolors of the drawing and he actuates in accordance the perforatingmachine. But experience has demonstrated that automatic reading devicesare quite defective in this respect and generate erroneous responses assoon as the number of different colors or dyes used in the drawingincreases.

. It has already been proposed to avoid these inconveniences byconsidering the spectral components of each dye in a system of primarycolors or wave lenghts (generally three, such as blue, green and red,but sometimes only two such as blue and red). The drawing or othersample is then illuminated by a beam of light of predeterminedcharacteristics and the intensity of the light which it reflects ismeasured by photo-electric means in the primary colors or wave lengthsselected. The intensities or responses thus obtained theoriticallyindividualize the dye. In other words, taking for instance the quitesimple two-color system, the responses of the photoelectric measuringdevices may be plotted as abscissae and ordinates and for eachdyetherewould thus be found a single representative point. But in actualpractice the responses of the photo-electric devices vary in accordancewith the density of the dye on the paper. Moreover commercial dyes arenot quite uniform in their characteristics. It results therefrom thatthe response for each primary color may vary between certain limits.Taking these limits into consideration, in a two-coordinate system therepresentation of each dye in the successive samples is no more a point,but a rectangle (in a three-coordinate system it would be aparallelipiped). As long as these rectangles (or parallelipipeds) do notintersect each other, the automatic recognition of the dyes remainspossible, but as soon as the number of dyes used in the drawing issomewhat high, as for instance exceeds four or five, such is no more thecase and it will be readily understood that when the point correspondingto the responses of the photo-electric devices is situated in the zonecommon to two rectangles (or parallelipipeds), any automatic recognitionbetween the corresponding dyes becomes quite impossible.

The present invention has for its object to greatly improve thepossibilities of recognition of the various dyes or colors of a designor other object.

In accordance with the present invention in a method for the recognitionof the various dyes used in a sample such as a drawing, of the kindwherein the sample is il luminated by a beam of light of predeterminedcharacteristics, the intensity of the light reflected by the samplebeing measured in a number of primary colors and the correspondingrepresentative point being situated in a system of coordinatescorresponding to the values measured in each primary color, the surfaceor volume' which forms the locus of the possible representative pointsof each dye taking into account the unavoidable variations of itsdensity and of its characteristics, is determined in the said coordinatesystem, lines or surfaces passing between the said loci are also drawnin the said system, and these lines or surfaces are analogicallyrepresented by electronic circuits in order that the position of therepresentative point of the dye with re spect to the said lines orsurfaces may be automatically detected for any sample being analyzed.

When only two primary colors are used the coordinate system is of thetwo-dimensional type and the loci corresponding to the various dyes aresurfaces which may be separated by straight lines or by successions ofsegments of straight lines. Such lines or segments may be easilyrepresented electronically. With three primary colors the coordinatesystem becomes threedimensional, the loci are volumes which must beseparated by planes or by successions of portions of such planes, andthe electronic representation is more difficult. In the case of morethan three primary colors it is still possible to imagine systemscomprising more than three coordinates, but thisstill more complicatesthe electronic circuits. In accordance with the present invention thesedifficulties are avoided by considering the primary colors by successivepairs, as for instance blue-green, green-red and red-blue in the case ofthree colors. Each pair thus corresponds to a quite simpletwo-dimensional system which only requires simple and inexpensiveelectronic circuits.

In the annexed drawings:

FIG. 1 shows in a diagrammatic manner how it has been proposed toindividualize a dye in a three-color system according to the Prior art.

FIG. 2 shows how such a representation does permit of differentiatingtwo dyes when no overlapping occurs.

FIG. 3 demonstrates that such a differentiation is impossible when thereis an overlapping in the three primary colors.

FIGS. 4 and 5 illustratehow the invention permits of differentiating twodyes in the case of two primary colors by means of a two-dimensionalsystem of coordinates.

FIGS. 6 and 7 illustrate in block form the electronic circuits adaptedto effect the automatic difierentiation between the two dyes in the caserespectively of FIG. 4 and of FIG. 5.

FIG. 8 is a two-dimensional representation similar to that of FIGS. 4and 5, but corresponding to the case of four dyes.

FIG. 9 shows in block form an electric circuit for the differentiationof the four dyes of FIG. 8.

FIG. 10 shows a circuit adapted to the case of three primary colors,i.e., wherein the representative point of a dye is situated in athree-dimensional system of coordinates.

FIGS. ll, 12 and 13 illustrate how the dyes may be represented in threetwo-dimensional systems of coordinates in the case of three primarycolors.

In the diagram of FIG. 1 the abscissae correspond to the wave lengthsand the ordinates to the light intensities. It has been assumed that thelight reflected from the drawing or other sample was analyzed in threeprimary colors, namely blue (b), green (v) and red (r). In other wordsthe sample (point of a drawing, for instance) receives a light flux ofknown characteristics and the intensity of the light reflected from thissample is measured in the three primary colors. If the coloring dye C ofthe sample were of perfectly uniform characteristics and if it wereapplied on the drawing with a quite uniform density, the intensities orresponses thus measured would always be constant for each primary color,whatever could be the sample bearing dye C. But in actual practice suchis not the case and on each ordinate b, v and r the points correspondingto the intensities vary respectively from b1 to b2, from v1 to v2 andfrom rl to r2. Thus it may be said that the three segments bl-b2, vl-v2and rl-r 2 are representative of the dye C.

If now another coloring dye C is submitted to the same operation, itwill be found that it may be represented by anotherset of three segmentsbl-b'2, v'l-v2 and r'l-r2 (see FIG. 2). If these three segments do notoverlap each other, the diagram of FIG. 2 permits the differentiation ofdyes C and C. It may even be remarked that this differentiation is stillpossible if there is an overlapping in two of the three primary colors.But if the segments overlap each other in the three colors, as shown inFIG. 3, any automatic differentiation becomes impossible when theresponses from the photo-electric elements are situated in theoverlapping zone.

Considering the problem from another point of view, the intensities orresponses measured in the three primary colors may be plotted in athree-coordinate system b, v, r, in which case segments bl-b2, vl-v2,rl-r2 and bl-b'2, v'l-v2, r'l-r'2 respectively define twoparallelipipeds. If the segments do not overlap each other in one atleast of the three primary colors, this means that the parallelipipedsare separate from each other and that therefore their differentiation isalways possible. On the contrary if the segments'overlap each other inthe three primary colors, the parallelipipeds intersect each other andany automatic differentiation is impossible for any point situated intheir common zone.

This inconvenience has hitherto limited automatic color differentiationin the prior art.

The present invention is based on the remark that when a sample bearingdye C gives the response bl in the primary color b, it will not at thesame time give response v2 in color v, but a response corresponding to apoint situated near v1. In other words the responses of a large numberof successive samples of the same dye in the three primary colors varymore or less in the same direction, though they are by no wayproportional. It results therefrom that in a three-coordinate system, b,v, r the representative points of a dye do not define a parallelipiped,but a much smaller volume situated within the parallelipiped.

For the sake of simplicity it is possible to consider first the case ofa two-color system b, r (FIG. 4). In such a system points b1, b2 and r1,r2 of FIG. 1 define a rectangle. But in fact when a large number ofdifferent samples of the same dye C1 are tested, it is found that therepresentative points are situated in a much smaller surface S1delimited by a closed curve which is tangent to the sides of therectangle. This surface may be considered as the locusof therepresentative points of the dye Cl. For another dye C2 there will befound another small surface S2. These surfaces 81 and S2 are ofelongated shape, as shown, and owing to their relatively reduced areathey are far less liable to intersect each other than the rectangleswhich would be defined by points bl, b2 and r1, r2, respectively b'l,b'2 and rl,

It may be remarked that a straight line such as P is represented by theequation:

in which x is the abscissa of the point where the lineintersects thex-axis, namely point A in FIG. 4.

There exists in the art adjustable gain amplifiers, or operationalamplifiers, which generate an outlet proportional to the differencebetween two voltages applied to their inlets. If a fixed voltagerepresenting the abscissa of point A is applied to the first inlet whilethe other inlet receives a variable voltage, and if the gain oftheamplifier is adjusted to a value representing the slope a in theequation, the outlet voltage of the amplifier will always represent theordinate of the point of line P which corresponds to the abscissarepresented by the variable voltage applied to the second inlet. If nowthis variable voltage is made equal to the response r of a sample of anunknown dye which may be either C1 or C2, the outlet voltage of theamplifier may be compared with the response b of the unknown dye and itmay thus be ascertained whether the representative point b, r of the dyeis above or below line P, or in other words if the said pointcorresponds to C1 or to C2.

FIG. 6 illustrates a circuit which may effect automatically the abovedifferentiation. An operational amplifier receives on its first inlet Ba voltage r which represents the response of the sample in the red,while a voltage r0 representing the abscissa of point A is applied toits second inlet C by means of a potentiometer 21. The gain of theamplifier is set at a by an auxiliary inlet g. Its outlet s thusrepresents the product a (r r0), i.e., the equation of line P. Thisoutlet is applied to the first inlet of a comparator 22 (which may beformed of another operational amplifier), the other inlet of whichreceives a signal brepresenting the repsonse of the sample in the blue.If the representative point of the sample, as determined by itsresponses b and r in the primary colors blue and red, weresituated online P, the outlet S of comparator 22 would be zero. In fact this outletwill be positive or negative thus indicating that the representativepoint is below or above line P (assuming that amplifier 20 andcomparator 22 generate a positive outlet when their first inlet is at ahigher level than their second one). Since the unknown dye is either C1or C2, the circuit of FIG. 6 will thus realize the differentiation ifthe outlet of 22 is negative, the unknown dye corresponds to surface S1and is therefore Cl, while if the outlet of 22 is positive, this dyewill be C2.

When surfaces S1 and S2 are separated from each other by a succession ofportions of straight lines, as for instance in FIG. 5, each line may beconsidered as a condition which may be represented by the outlet of acircuit such as that of FIG. 6. In the case illustrated in FIG. 7 eachelementary circuit comprises an operational amplifier, respectively 200and 20R which receives signals r and r0, and a comparator 220,respectively 22R receiving the outlet of the amplifier and signal b. Theoutlets of these comparators are applied to an appropriate gate 23 theoutlet of which individualizes dyes Cl and C2 (i.e., surfaces S1 andS2). In the case illustrated in FIG. 5 surface 82 is below both lines Qand R and therefore for any point of this surface the outlets of 220 and22R should both be positive. If gate 23 is of the AND type, it willtherefore emit a positive outlet whenever the unknown sample is of typeC2. The outlet of 23 may further be applied to the inlet of an inverter24 if it is desired to also obtain a positive signal to identify surface81 (i.e., dye C1).

The above explanations also apply to the case of more than two types ofdye, provided their representative surfaces or loci do not intersecteach other. FIG. 8 illustrates for instance the case of four dyes C1,C2, C3, C4, i.e., of four surfaces S1, S2, S3, S4 separated by threelines T, U, V. Considering the representative point of an unknown dyeand assuming that the outlet ST, SU, SV (FIG. 9) of each'circuit'corresponding toa given line is negative when the representative pointof the unknown dye is above the said line, the differentiatingconditions will be as follows:

for dye C1 (surface S1) outlets ST, SU and SV negative (or more simplyST negative). for dye C2 (surface S2) outlet ST positive, outlets SU andSV negative (or more simply ST positive and SU negative). for dye C3(surface S3) outlets ST, SU positive, outlet SV negative (or more simplySU positive and SV negative) for dye C4 (surface S4) outlets ST, SU andSV positive (or more simply SV positive).

FIG. 9 shows how these conditions may be ascer tained electronically bymeans of four gates 2581, 2582, 2583 and 2584 to which outlets ST, SUand SV are applied. Gate 2581 may be of the NAND type so as to onlygenerate a positive outlet signal when all its inlets are positive. Asto gates 2582 and 2583, they may be of either type provided an inverteris inserted on one or two of their three inlets. For instance 2582 maybe of the NAND type if an inverter is inserted between its first inletand comparator 221. It will also be apparent that gate 2581 may bereplaced by a mere inverter receiving outlet ST, that the third inlet of2582 may be omitted, etc... In any case the individual outlets of gates2581, 2582, 2583 and 2584 fully identify the four dyes.

It has been hitherto assumed that only two primary colors (blue and red)were used to identify the dyes. In the case of three primary colors orwave lengths, the locus of the representative points of each dye is nomore a surface, but a volume. But here again these volumes generally donot intersect each other and therefore it is possible to separate themby intermediate surfaces, practically speaking by planes or portions ofplanes. Each plane may be represented by an equation which may be inturn analogically represented by electric circuits of the type describedwith reference to FIG. 6.

FIG. 10 illustrates a circuit corresponding to three primary colors,namely blue b, green v and red r. A first operational amplifier 251receives signal or response v and an adjustable signal v0. Its gain isg1. Its outlet s1 is applied to the second inlet of another operationalamplifier 252 the first inlet of which receives signal r. The gain ofthis amplifier is g2. The outlet :2 of 252 is applied to the first inletof a third operational amplifier 253 having a gain g3 and which receiveson its second outlet the signal b. The outlet S of 253 is the generaloutlet of the circuit. It is obvious that:

.91 gl.( vv 0) s2 g2 r sll S g3 s2 b and therefore:

S 33 (rg2 vg1g2 v0g1g2 b).

The general outlet voltage S thus becomes zero for any point thecoordinates b, v, r of which are such that:

This equation corresponds to a plane in a threecoordinate system. Itresults therefrom that when the responses b, v, r corresponding to anunknown dye are applied to the circuit of FIG. 10, the sign of theoutlet S will indicate on whichside of this plane the representativepoint of the said dye. is situated in the threecoordinate system b, v,'r.

The above explanations may be extended to the case of any number ofprimary dyes. For instance with four dyes it is possible to imagine afour-dimensional space and therefore a four-coordinate system in whichthe locus of each dye is a four-dimensional volume, these volumes beingseparated from each other by threedimensional surfaces.

But it is generally possible to avoid the intricate representation ofvolumes, and more particularly of volumes having more than threedimensions, by considering the primary colors in successive pairs. Forinstance in the case of three primary colors these pairs will be bv, vrand rb. Each pair may be represented in a twocoordinate system which maybe considered as the projection of the three-coordinate system b, v, ron one of the three planes defined by the three coordinate axes. Thedifferentiation thus obtained is less perfect since it may occur thattwo volumes which do not intersect each other in the three-dimensionalspace, have their projections intersecting each other in the saidplanes. But this is rather unfrequent and on the other hand theelectronic equipment required is greatly simplified.-

FIGS. 11 to 13 illustrate the .case of two dyes with three primarycolors b, v, r. In the first two-dimensional system bv (FIG. 11) thesurfaces or loci 8'1 and S'2 intersect each other and therefore do notpermit a safe differentiation. In the system vr the correspondingsurfaces S"l and S"2 are admittedly spaced from each other, but theycannot be separated by a single straight line and two lines W and X mustbe used, which would somewhat complicate the electronic equipment. Butin the third system rb the corresponding surfaces S" l and S" 2 may beseparated by a single straight line Y which besides may pass through theintersection of the coordinate axes andtherefore be represented by aquite simplified electronic circuit.

It is obvious that the same method may be applied to more than threeprimary colors or wave lengths, here again provided that if the volumesor loci of the various dyes C1, C2, C3, etc. do not intersect eachother, their projections in the planes of the coordinate axes also donot intersect each other in one at least of the said planes.

It should be remarked in this repsect that differentiation is onlyimpossible when the intersection concerns the same dyes in all theplanes. in other words with the three primary colors and, say, four dyesC1, C2, C3, C4, differentiation is impossible when for instance thesurfaces or loci ofCl and C2 intersect each other in the three planesb-v, v r and r-b. But it remains quite possible if for instance thelocus of C1 intersects the locus of C2 in planes b-v and v-r, butintersects another cus, as for instance that of C3, in plane r-b. It isindeed clear that in such a case the representative point of the unknowndye cannot be included in the two same surfaces or loci in the threetwo-dimensional systems.

I claim:

1. In a method for the automatic recognition of the coloring dyes usedin a sample such as a drawing for the preparation of the perforatedcards or bands for loom Jacquards, by means of photo-sensitive meanswhich analyze in a number of primary colors or wave lengths the lightreflected by each of the dyes to be recognized when the correspondingportion of the sample is illuminated by a light beam of predeterminedcharacteristics, recognition of each dye from which the light isreflected being based on the position of the point which represents theresponses of the photo-sensitive means corresponding to each of saidprimary colors in a system of coordinates in which each axis correspondsto one of said primary colors, the response of each of saidphoto-sensitive means being plotted along the one of said axes whichcorresponds to the same primary color,

the improvement which consists in 'asiermi'sihgtaiesch sr'said'a'yss to'be recognized the permissible variations in its color attribrites andin its density on the sample in said coordinate system; in determiningin said system of coordinates the locus of all the possible pointsrepresentative of the color attribrites and density of each of said dyesto be recognized, taking into account said permissible variations, tothus obtain a number of loci equal to the number of said dyes;

in draw iiig' i n 'sardine."sresaraisaiss' at least' one geometricalfigure which separates from each other the loci of the dyes to berecognized, said figures having a dimension less than said loci;

in analogically representing each of said figures by an electroniccircuit so as to obtain a number of circuits equal to the number of saidseparating figures, each of said circuits, when receiving inlet signalscorresponding to the color of a dye expressed by the coordinates of apoint in said system, emitting an outlet signal at a predetermined levelwhen said last-named point is part of the separating figure representedby said last-named circuit, at a level above said predetermined levelwhen said last-named point is situated on one side of said last-namedfigure, and at a level below said predetermined level when saidlastnamed point is on the other side of said lastnamed separatingFigure;

in applying as inlet signals to each of said circuits the responses ofsaid photo-sensitive means;

and in determining from the levels of the outlet signals of saidelectronic circuits the location of the representative point of the dyeto be recognized with respect to the location of said figures.

2. In a method as claimed in claim 1:

said primary colors being two in number;

said system of coordinates being two-dimensional;

each of said loci being a surface delimited by a closed curve;

and some at least of said separating figures being formed 'of a straightline.

3. In a method as claimed in claim 1:

said primary colors being two in number;

said system of coordinates being two-dimensional;

each of said loci being a surface delimited by a closed curve;

and some at least of said separating figures being formed of asuccession of segments of different straight lines.

4. In a method as claimed in claim 1:

said primary colors being three in number;

said system of coordinates being three-dimensional;

I each of said loci being a volume delimited by a surface closed onitself;

and some at least of said separating figures being formed of a plane.

5. in a method as claimed in claim 1:

said primary colors being three in number;

said system of coordinates being three-dimensional;

each of said loci being a volume delimited by a surface closed onitself;

and some at least of said separating figures being formed of asuccession of portions of different planes.

6. in a method for the automatic recognition of the coloring dyes usedin a sample such as a drawing for the preparation of the perforatedcards or bands for loom Jacquards, by means of photo-sensitive meanswhich analyze in more than two primary colors or wave lengths the lightreflected by each of the dyes to be recognized when the correspondingportion of the sample is illuminated by a light beam of predeterminedcharacteristics, recognition of each dye from which the light ifreflected being based on the responses of the photosensitive meanscorresponding to each of said primary colors,

the improvement which consists:

in determining the representative point which corresponds to theresponses of said photo-sensitive means for each pair of said primarycolors in a two-dimensional system of coordinates in which each axiscorresponds to one of the primary colors of said each pair, by plottingthe response of each of said last-named photo-sensitive means along theone of said axes which corresponds to the same primary color for eachdye, so as to obtain a number of two dimensional systems equal to thepossible number of pairs of said primary colors with'each of said dyesto be recognized being represented in each of said systems;

in determining for each of said dyes to be recognized the permissiblevariations in its color attribrites and in its density on the sample;

indglgrrniningin each of said two-dimensional sysmm of coordinates thecurve which delimits the locus of all the possible representative pointsof each of said dyes to be recognized, taking into account thepermissible variations I of same;

in drawing in each of said two-dimensional systems of coordinates lineswhich separate from each other the loci of said dyes to be recognized;

9 10 in analogically representing each of said lines by an the twoprimary colors corresponding to the one electronic circuit means forobtaining in each of of said two-dimensional systems which includes Saidtwo-dimensional Systems a number of the one of said separating lines towhich said lastcuits equal to the number of separating lines, named i itcorresponds;

each of said circuits, when receiving inlet signals corresponding to thecoordinates of a point in said last-named system, emitting an outletsignal at a predetermined level when said last-named point is part ofthe separating line represented by said last-named circuit, at a levelabove said preand in determining from the level of the outlet signals ofsaid electronic circuits between each of said separating lines therepresentative point of each dye to be recognized is situated in some atleast of said two-dimensional systems of coordidetermined level whensaid last-named point is nates' I I Situated on one Side of saidlastmamed line and 7. In a method as claimed lIl claim 6, some at leastof at a level below said predetermined level when said separatmg [mes gf linessaid last-named point is on the other side of said In a methodClalmed clalm some at least last-nam d se i li 15 said lines beingformed of a succession of segments of in applying as inlet signals toeach of said circuits different straight lines.

the responses of said photo-sensitive means in

1. In a method for the automatic recognition of the coloring dyes usedin a sample such as a drawing for the preparation of the perforatedcards or bands for loom Jacquards, by means of photo-sensitive meanswhich analyze in a number of primary colors or wave lengths the lightreflected by each of the dyes to be recognized when the correspondingportion of the sample is illuminated by a light beam of predeterminedcharacteristics, recognition of each dye from which the light isreflected being based on the position of the point which represents theresponses of the photo-sensitive means corresponding to each of saidprimary colors in a system of coordinates in which each axis correspondsto one of said primary colors, the response of each of saidphoto-sensitive means being plotted along the one of said axes whichcorresponds to the same primary color, the improvement which consists indetermining for each of said dyes to be recognized the permissiblevariations in its color attribrites and in its density on the sample insaid coordinate system; in determining in said system of coordinates thelocus of all the possible points representative of the color attribritesand density of each of said dyes to be recognized, taking into accountsaid permissible variations, to thus obtain a number of loci equal tothe number of said dyes; in drawing in said system of coordinates atleast one geometrical figure which separates from each other the loci ofthe dyes to be recognized, said figures having a dimension less thansaid loci; in analogically representing each of said figures by anelectronic circuit so as to obtain a number of circuits equal to thenumber of said separating figures, each of said circuits, when receivinginlet signals corresponding to the color of a dye expressed by thecoordinates of a point in said system, emitting an outlet signal at apredetermined level when said last-named point is part of the separatingfigure represented by said last-named circuit, at a level above saidpredetermined level when said last-named point is situated on one sideof said last-named figure, and at a level below said predetermined levelwhen said last-named point is on the other side of said last-namedseparating Figure; in applying as inlet signals to each of said circuitsthe responses of said photo-sensitive means; and in determining from thelevels of the outlet signals of said electronic circuits the location ofthe representative point of the dye to be recognized with respect to thelocation of said figures.
 2. In a method as claimed in claim 1: saidprimary colors being two in number; said system of coordinates beingtwo-dimensional; each of said loci being a surface delimited by a closedcurve; and some at least of said separating figures being formed of astraight line.
 3. In a method as claimed in claim 1: said primary colorsbeing two in number; said system of coordinates being two-dimensional;each of said loci being a surface delimited by a closed curve; and someat least of said separating figures being formed of a succession ofsegments of different straight lines.
 4. In a method as claimed in claim1: said primary colors being three in number; said system of coordinatesbeing three-dimensional; each of said loci being a volume delimited by asurface closed on itself; and some at least of said separating figuresbeing formed of a plane.
 5. In a method as claimed in claim 1: saidprimary colors being three in number; said system of coordinates beingthree-dimensional; each of said loci being a volume delimited by asurface closed on itself; and some at least of said separating figuresbeing formed of a succession of portions of different planes.
 6. In amethod for the automatic recognition of the coloring dyes used in asample such as a drawing for the preparation of the perforated cards orbands for loom Jacquards, by means of photo-sensitive means whichanalyze in more than two primary colors or wAve lengths the lightreflected by each of the dyes to be recognized when the correspondingportion of the sample is illuminated by a light beam of predeterminedcharacteristics, recognition of each dye from which the light ifreflected being based on the responses of the photo-sensitive meanscorresponding to each of said primary colors, the improvement whichconsists: in determining the representative point which corresponds tothe responses of said photo-sensitive means for each pair of saidprimary colors in a two-dimensional system of coordinates in which eachaxis corresponds to one of the primary colors of said each pair, byplotting the response of each of said last-named photo-sensitive meansalong the one of said axes which corresponds to the same primary colorfor each dye, so as to obtain a number of two dimensional systems equalto the possible number of pairs of said primary colors with each of saiddyes to be recognized being represented in each of said systems; indetermining for each of said dyes to be recognized the permissiblevariations in its color attribrites and in its density on the sample; indetermining in each of said two-dimensional systems of coordinates thecurve which forms the locus of all the possible representative points ofeach of said dyes to be recognized, taking into account the permissiblevariations of same; in drawing in each of said two-dimensional systemsof coordinates lines which separate from each other the loci of saiddyes to be recognized; in analogically representing each of said linesby an electronic circuit means for obtaining in each of saidtwo-dimensional systems a number of circuits equal to the number ofseparating lines, each of said circuits, when receiving inlet signalscorresponding to the coordinates of a point in said last-named system,emitting an outlet signal at a predetermined level when said last-namedpoint is part of the separating line represented by said last-namedcircuit, at a level above said predetermined level when said last-namedpoint is situated on one side of said last-named line, and at a levelbelow said predetermined level when said last-named point is on theother side of said last-named separating line; in applying as inletsignals to each of said circuits the responses of said photo-sensitivemeans in the two primary colors corresponding to the one of saidtwo-dimensional systems which includes the one of said separating linesto which said last-named circuit corresponds; and in determining fromthe level of the outlet signals of said electronic circuits between eachof said separating lines the representative point of each dye to berecognized is situated in some at least of said two-dimensional systemsof coordinates.
 7. In a method as claimed in claim 6, some at least ofsaid separating lines being straight lines.
 8. In a method as claimed inclaim 6, some at least of said lines being formed of a succession ofsegments of different straight lines.